+1. This is how I feel about tethering also. I have used it a few times when I'm on the road with no wifi nearby but only for work related stuff that I can't do on the Droid. I'm sure you can use this much or more watching a ton of YouTube videos or using Pandora 24/7 but those things don't violate the ToS. It specifically says we are not allowed to tether our Droid's to any internet capable device for data usage. The Palm mobile hot spot is different, it is specifically for Palm devices.
You may be on the radar now, so just be safe and don't tether for awhile. They can very easily see what type of data you have been accessing from a simple interface they have available. If they see any torrent stuff, online gaming, windows updates, application downloads for pc's and so on then they will flag your account, after that they will go through it with a fine tooth comb and every MB of data you used via tethering will net you some extra charges.